The present invention relates to decorators used to apply ink to containers including but not limited to cans, plastic containers and the like. More specifically, the present invention relates to a system and method for controlling the temperature of ink used in a decorator.
Cylindrical containers such as cans are often decorated using ink applied by high speed machines called decorators. The decorators can operate at high speeds and can be configured to process over 2000 objects per minute. As such, they are configured to apply a multi-color ink pattern or print image having two or more colors by rotating the cylindrical container past a printing blanket loaded with ink.
Typical decorators have a number of mandrels arrayed on the periphery of a mandrel wheel. The mandrels are each configured to support an individual object such as a can so that the objects can continually rotate around the axis of the mandrel wheel. The mandrel wheel turns in coordination with a blanket wheel that is configured with a number of printing blankets arranged around the periphery of the blanket wheel to engage the objects positioned on the mandrels located on the mandrel wheel. Each printing blanket rotates past one or more inker rolls to pick up a volume of ink with each individual inker roll, applying a different color ink based upon the desired final print image.
After the printing blanket has been inked, the printing blanket rotates past and contacts an object to transfer the ink image to the object's surface. The mandrel wheel can advance the object past additional printing blankets to impart the decorated surface as desired or required. Once the design has been printed on the object, the object can be advanced to suitable post-printing processing stations such as varnishing and curing operations. The printing blanket(s) continue to rotate with the associated blanket wheel and the process can be repeated on subsequent objects.
The various printing blanket(s) are supplied with ink in a continuous repeatable manner. In certain devices, each inker device contains a number of rollers that transfer ink from an ink reservoir such as an ink tray or ink fountain to the printing blanket located on the blanket wheel. Eventually the ink is transferred to a suitable printing plate cylinder.
One challenge associated with using decorators operating at high speeds is maintaining the ink at proper temperature. In order achieve successful high-speed ink application, each individual ink composition should be maintained within an optimum temperature range. Deviation outside this prescribed optimum temperature range can alter physical and/or chemical properties of the ink composition can result in improper image transfer. For example, elevated ink temperature can lead to volatilization of ink components of the ink that can alter the ink chemistry. Similarly application temperatures below optimum can alter the viscosity of the composition of one or more or the constituent parts of ink. Temperatures that are below optimal can result in phenomena such as misting or slinging. Temperature variations can lead to changes in color hue and intensity. Temperature changes can also lead to improper or irregular deposition of ink material including but not limited to runs bleeds and the like.
Image transfer difficulties can occur at system startup or restart as the various inks are brought to temperature. Other difficulties are encountered during system operation. During prolonged high-speed operation, temperatures of the various component parts of the applicator as well as the associated inks can exceed optimum recommended application temperatures. The application temperatures of the various inks can also be affected by fluctuations in surrounding ambient temperature in certain applications.
Various temperature control systems have been proposed to minimize the amount of time that the temperature of the ink is outside the desired temperature range. These systems provide a central ink temperature conditioning system composed of a central recirculation loop that is configured to recirculate a temperature conditioning solution and a feeder line that controls the flow of the temperature conditioning solution and delivers it to a remote location located on at least one ink roller on a decorator. The system is configured to deliver temperature conditioning solution that includes a dedicated a heating solution or a dedicated cooling solution to the plurality of ink rollers based on the detected temperature of the ink to be applied.
Such systems typically circulate water through the various rollers to control temperature and typically pass water through a rotary union into a bore prepared in a shaft that extends under the entire width of the associated roller. Holes bored through the shaft perpendicular to its axis near each end of the roller are intended to allow the water to flow through the hollow body of the roller to transfer heat away from the associated assembly. Water circulation is controlled via a pump located remote from both the circulation conduits and the printing blanket(s).
Heretofore the various systems required large control loops and operated on a manually controlled duty-cycle model. It would be desirable to provide a system that provides an automated system that provides a closed loop system that is feedback controlled and is proximate to the inker. It would also be desirable to provide a modular decorator temperature control system that allows the temperature of the ink being applied to a container to be accurately controlled in a small, easy-to-install interface mounted directly to the inker station providing local control of temperature at the point of use.